diff --git a/knockout/knockout.d.ts b/knockout/knockout.d.ts
index d67e96a186..dba3fc36f6 100644
--- a/knockout/knockout.d.ts
+++ b/knockout/knockout.d.ts
@@ -134,6 +134,7 @@ interface KnockoutBindingHandler {
     init? (element: any, valueAccessor: () => any, allBindingsAccessor: KnockoutAllBindingsAccessor, viewModel: any, bindingContext: KnockoutBindingContext): void;
     update? (element: any, valueAccessor: () => any, allBindingsAccessor: KnockoutAllBindingsAccessor, viewModel: any, bindingContext: KnockoutBindingContext): void;
     options?: any;
+    preprocess?: (value: string, name: string, addBindingCallback?: (name: string, value: string) => void) => string;
 }
 
 interface KnockoutBindingHandlers {